New methods of cell cycle analysis are being developed and applied to a variety of experimental systems in an effort to better understand the malignant process and to optimize the treatment of cancer by chemotherapy and radiotherapy. 1. The fraction of labeled mitosis (FLM) method will be pursued, including the provision of a service for computer analysis of FLM data and the compilation and interpretation of FLM results. 2. Cell dispersal and staining techniques will be developed to reduce solid tissues to cell suspensions suitable for flow analysis and sorting. 3. Flow systems (flow cytometry and cell sorting) methods will be applied to cell cycle analysis of perturbed and unperturbed cell populations. a. Computer programs will be developed to automatically extract kinetic parameters from flow system data. b. The flow system techniques of cell cycle analysis will be applied to cells from solid tissues as dispersal techniques improve. c. Detailed comparisons of the kinetic behavior of normal and perturbed cells will be continued. BIBLIOGRAPHIC REFERENCES: Mendelsohn, M.L., Computer-Analyzed Transit Times for Vertebrate Cell Cycle and Phases, (In) Cell Biology (P.L. Altman and D.D. Katz, eds.), Federation of American Societies for Experimental Biology, Bethesda, Maryland (1976). Mendelsohn, M.L., Principles, Relative Merits and Limitations of Current Cytokinetic Methods. (In) Symposium Monograph Growth Kinetics and Biomedical Regulation of Normal and Malignant Cells, Houston, Texas, 10-12 March (1976). In press.